1. Field of the Invention
The present invention relates to an acceleration tube conditioning system with an acceleration tube conditioning apparatus and an acceleration tube conditioning method.
2. Description of the Related Art
There are known acceleration tubes to accelerate charged particles such as electrons. Such acceleration tubes are applied to a radiotherapy system, a non-destructive inspection system, and a sterilization system. In the radiotherapy system, therapeutic radiation generated by bremsstrahlung of the accelerated electrons is irradiated to a deceased area (or tumors) in order to treat patients. In the non-destructive inspection system, radiation generated by bremsstrahlung of the accelerated charged particles transmits an inspection target and transmission images are obtained for examination of the examination target. In the sterilization system, the accelerated charged particles are irradiated onto a sterilization target or radiation generated by bremsstrahlung of the accelerated charged particles is irradiated onto a sterilization target in order to sterilize the sterilization target.
In such an acceleration tube, a plurality of electrodes are provided to accelerate charged particles which are inputted into an acceleration tube and accelerated with high frequency power applied to the acceleration tubes. In such an acceleration tube, conditioning (i.e., aging operation) is performed before using charged particles. The conditioning is a process of cleaning the internal surface of the tube by supplying high frequency power to the acceleration tube while vacuuming an atmosphere inside the tube, to generate appropriate arc discharge on a surface of internal walls of the acceleration tube so that some kind of contaminants and electron emitter absorbed in the surface can be removed (for example, refer to “Automated High-Power conditioning of medical accelerators” (Proceedings of EPAC 2004) by S. M. Hanna, et. al.
The conditioning process is performed continuously day and night to allow continuous maintenance of a high surface activity state of the acceleration tube, so that a process can be efficiently performed. The conditioning process is performed in manual, by detecting an RF reflection wave visually, by monitoring a current of an ion pump provided in the acceleration tube to confirm generation of discharge, and by changing a high frequency input condition into the acceleration tube. In this manual operation, a work load is high and there are variations in a change time and a change amount depending on persons, so that it is difficult to sustain a constant process condition. Automatic implementation of such a conditioning process of an acceleration tube is demanded, and a more certain conditioning process of the acceleration tube is demanded.